1. Technical Field
The present invention relates to stators for rotating electric machines that are used in, for example, motor vehicles as electric motors and electric generators.
2. Description of Related Art
There are known rotating electric machines that are used in motor vehicles as electric motors and electric generators. These rotating electric machines generally include a rotor and a stator. The rotor is rotatably provided and functions as a field. The stator is disposed in radial opposition to the rotor and functions as an armature.
Japanese Patent Application Publication No. JP2013162636A discloses a stator for a rotating electric machine. The stator is formed by assembling a plurality of stator pieces into an annular shape. Each of the stator pieces includes a coil that is formed by winding an electric conductor wire around a bobbin, and a stator core having teeth to which the coil is mounted. Moreover, in the patent document, there is also disclosed a power distribution component that is designed to reduce the number of types of connection terminals connecting busbars and the coils of the stator, thereby reducing the manufacturing cost.
There are also known two methods of winding a coil on a stator core, namely, concentrated winding and distributed winding. Concentrated winding is a winding method in which the coil is wound so as to be concentrated in one slot of the stator core, as disclosed in the above patent document. On the other hand, distributed winding is a winding method in which the coil is wound so as to be distributed to a plurality of slots of the stator core.
Compared to concentrated winding, distributed winding is more advantageous in terms of torque improvement and noise reduction. However, at the same time, distributed winding has a disadvantage such that the distance between each circumferentially-adjacent pair of the slots of the stator core is short. Therefore, in the case of joining lead wires to power and neutral wires by welding, the distance between each circumferentially-adjacent pair of the resultant welds is accordingly short; the lead wires are led out from a coil end part of a stator coil which protrudes from an axial end face of the stator core. Consequently, creeping discharge may occur between the welds, resulting in insulation failure.